1. Field of the Invention
The present invention relates to a robot numerical control apparatus capable of following an operation directed from a program and utilizing, in such program, the processed result of an image formed by a television camera disposed in the vicinity of a manipulating end of the robot. And more particularly the invention relates to an improved control apparatus which is capable of shifting the center of the image to a desired position with pseudo control of positioning such image center at the manipulating end of the robot so as to achieve an enhanced precision in the image forming action.
2. Description of the Prior Art
In the latest technical stage relative to assembly of electronic appliances where extremely high precision and miniaturization of component parts are required, it is difficult to ensure the absolute accuracy with regard to the position for feeding the component parts.
In an attempt to avert such difficulties, it is generally customary to adopt a method of installing a television camera in the vicinity of a portion of a robot used for an assembling work, then processing the image obtained from the television camera, and performing the assembly while correcting the feed position and so forth in accordance with the result of such process.
In most of the conventional cases, a robot numerical controller and an image processor are provided individually, and the coordinate system employed for the numerical controller and that for the image processor are independent of each other.
Therefore it is usual to adopt such a technique whereby the robot numerical controller accepts the result of the image processing and, after transforming the same to the coordinate system relevant to the numerical controller, actuates the robot on the basis of the result thus transformed.
However, according to the method mentioned, it becomes necessary to write a program for coordinate transformation in the robot operating program which is extremely complicated in practical use.
Even in a case where coordinate transformation is rendered expressible in a plain notation by modifying the programming language (e.g., in a case where the description relative to the transformation is expressed by a subroutine), the principle of operation remains unchanged since the robot is actuated on the basis of the sensed input image. Consequently, recognition of any article in the periphery of the image is hampered by the aberration of the lens and so forth to eventually require an expensive lens to attain a satisfactory high precision.
Although low-cost solid-state image pickup devices such as small-sized CCD area image sensors are available of late, it is occasionally necessary to employ, in low-luminance photography for example, a conventional image pickup device such as reticon tube. And in most cases some distortion is unavoidable in the periphery of the sensed image to consequently fail to meet the requirements of a high precision process.
For averting the above problems (intricacy in the programming and difficulties concerned with the image processing precision), it is necessary, in sensing the image, to place a subject or component part, which is to be assembled, at the center of the entire image. However, the conventional system known heretofore determines the operation of the robot based on the sensed image, so that when the robot is to be actuated for positively catching and photographing the subject at the center of the image, it is rendered impossible to directly indicate the desired displacement position to the center of the sensed image. In this case, it is necessary to calculate at predetermined time intervals the desired displacement position of the robot's manipulating end corresponding to the desired displacement position of the center of the image on the basis of the positional relationship between the camera and the robot's manipulating end, and then to write in the program a command for moving the manipulating end of the robot. Therefore, if a considerably long time is required for such calculation, it becomes impossible to shorten the processing time.